1. Field of the Invention
The present invention relates to a machine and a method for exchanging old ties of a railroad track for new ties, the track being comprised of two rails fastened to the ties defining cribs therebetween, which comprises a machine frame supported by undercarriages for mobility along the track, a longitudinally, vertically and transversely displaceable tie exchange device connected to the machine frame for laterally pulling the old ties out of the track and laterally inserting the new ties in the track at a tie exchange position, a ballast scarifying device for clearing ballast at the tie exchange position, and a device for depositing the ties.
Throughout the specification and claims, the directional terms "transversely" and "longitudinally" refer to the direction with respect to the longitudinal extension of the track.
2. Description of the Prior Art
European patent No. 0 057 128, published Aug. 4, 1982, discloses a tie exchanging machine of this general type, which comprises a tie exchange device for pulling the old ties and inserting the new ties, a vertically adjustable excavator for clearing the ballast at the tie exchange site, a tie depositing device, a ballast storage bin, a ballast tamper, a ballast broom and a ballast plow. The tie depositing device facing one side of the tie exchange device is comprised of two parallel, horizontal and longitudinally extending roller conveyors. While one of the roller conveyors transports the new ties to the tie exchange device, the other conveyor transports the old ties from the tie exchange device. The tie exchange device is longitudinally displaceably mounted on the machine frame and moves the old ties to, and the new ties from, the respective roller conveyors, the ties being turned 90.degree. between their transverse positioning at the tie exchange site and their longitudinal positioning on the roller conveyors. This turning of the ties and the required centering of the ties on the roller conveyors considerably complicates and slows the operation.
U.S. Pat. No. 4,955,301, dated Sep. 11, 1990, discloses a tie exchange train comprising a series of bridge-like machine frames coupled to each other and carrying different tie exchange devices longitudinally displaceably mounted on the machine frames. The old ties are removed by a tie exchange device at the front of the train and the new ties are inserted by a tie exchange device at the rear of the train. The tie exchange devices are arranged on a longitudinally extending auxiliary carrier which is longitudinally displaceable and has one end supported on the railroad track by an undercarriage while an opposite auxiliary carrier end is pivotally supported on the machine frame. The old ties are deposited from the tie exchange device withdrawing the old ties from the track on a conveyor band extending below the auxiliary frame. The conveyor band conveys the old ties from an end of the conveyor band adjacent the tie exchange device to an opposite conveyor band end where they are transferred to an ascending conveyor. The old ties collected on the ascending conveyor are conveyed to a storage area on top of the machine frame where the old ties are stacked. The stack of old ties is then removed by means of a mobile crane which is mounted on, and runs along, the train. The new ties are similarly, and in reverse order, conveyed to the tie exchange device which inserts the new ties in the track. This machine very efficiently exchanges ties in an assembly line mode while the train continuously advances along the track, groups of three or four adjacent ties being exchanged in this fashion. However, such a train is not useful when a smaller machine unit with a single tie exchange device for withdrawing and inserting ties is desired.
U.S. Pat. No. 4,794,861, dated Jan. 3, 1989, U.S. Pat. No. 4,829,907, dated May 16, 1989, and U.S. Pat. No. 4,884,509, dated Dec. 5, 1989, disclose tie exchange trains of the above-described type, including transport cars for the ties and a mobile tie loading and unloading crane which may be driven longitudinally along the track.